from django.db.models import F
from django.http import HttpResponse, HttpResponseRedirect
from django.template import loader
from .models import Question, Choice
from django.shortcuts import render, get_object_or_404
from django.http import Http404
from django.urls import reverse
from django.views import generic
from django.utils import timezone
# def index(request):
#     latest_question_list = Question.objects.order_by("-pub_date")[:5]
#     # template = loader.get_template("polls/index.htnl")
#     context = {"latest_question_list": latest_question_list}
#     # return HttpResponse(template.render(context, request))
#     return render(request, "polls/index.html", context)

# def detail(request, question_id):
#     # return HttpResponse( "You're looking at the results of question %s." % question_id)
#     # try:
#     #     question = Question.objects.get(pk=question_id)
#     # except Question.DoesNotExist:
#     #     raise Http404("Question does not exist")
#     # return render(request, "polls/detail.html", {"question": question})

#     question = get_object_or_404(Question, pk=question_id)
#     return render(request, "polls/detail.html", {"question": question})

# def results(request, question_id):
#     question = get_object_or_404(Question, pk=question_id)
#     return render(request, "polls/results.html", {"question": question})


# 替换为通用视图 
class IndexView(generic.ListView): 
    template_name = "polls/index.html" 
    context_object_name = "latest_question_list"

    def get_queryset(self):
        # """Return the last five published questions."""
        # return Question.objects.order_by("-pub_date")[:5]
        """
        Return the last five published questions (not including those set to be
        published in the future).
        """
        return Question.objects.filter(pub_date__lte=timezone.now()).order_by("-pub_date")[:5]


class DetailView(generic.DetailView):
    model = Question
    template_name = "polls/detail.html"
    def get_queryset(self):
        """
        Excludes any questions that aren't published yet.
        """
        return Question.objects.filter(pub_date__lte=timezone.now())


class ResultsView(generic.DetailView):
    model = Question
    template_name = "polls/results.html"

def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])

    except (KeyError, Choice.DoesNotExist):
        return render(
            request,
            "polls/details.html",
            {
                "question": question,
                "error_message": "You didn't select a choice.",
            },
        )
    else:
        selected_choice.votes = F("votes") + 1  # 指示数据库将投票数增加 1
        selected_choice.save()

    # 成功处理POST数据后，总是应该返回一个HttpResponseRedirect
    return HttpResponseRedirect(reverse("polls:results", args=(question.id, )))